回复: [PATCH v4 04/13] LoongArch: ABI Implementation
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从 Windows 版邮件发送
发件人: Fangrui Song
发送时间: 2022年5月9日 16:24
收件人: caiyinyu
抄送: libc-alpha@sourceware.org; xuchenghua@loongson.cn; joseph_myers@mentor.com
主题: Re: [PATCH v4 04/13] LoongArch: ABI Implementation
>+/* Runtime address of .got */
>+#define _GLOBAL_OFFSET_TABLE_ \
>+ ({ \
>+ ElfW (Addr) * r; \
>+ asm("la.pcrel %0, _GLOBAL_OFFSET_TABLE_" : "=r"(r)); \
>+ r; \
>+ })
>+
>+/* Return the link-time address of _DYNAMIC. */
>+static inline ElfW (Addr) elf_machine_dynamic (void)
>+{
>+ return _GLOBAL_OFFSET_TABLE_[0];
>+}
_GLOBAL_OFFSET_TABLE_[0] == link_time_dynamic is not recommended.
See
https://maskray.me/blog/2021-09-05-build-glibc-with-lld#global_offset_table_0
aarch64/riscv/x86_64/etc have been updated to use the preferred
approach.
Fixed.
>
Comments
On 2022-05-24, caiyinyu@loongson.cn wrote:
>
>
>从 Windows 版邮件发送
>
>发件人: Fangrui Song
>发送时间: 2022年5月9日 16:24
>收件人: caiyinyu
>抄送: libc-alpha@sourceware.org; xuchenghua@loongson.cn; joseph_myers@mentor.com
>主题: Re: [PATCH v4 04/13] LoongArch: ABI Implementation
>
>>+/* Runtime address of .got */
>>+#define _GLOBAL_OFFSET_TABLE_ \
>>+ ({ \
>>+ ElfW (Addr) * r; \
>>+ asm("la.pcrel %0, _GLOBAL_OFFSET_TABLE_" : "=r"(r)); \
>>+ r; \
>>+ })
>>+
>>+/* Return the link-time address of _DYNAMIC. */
>>+static inline ElfW (Addr) elf_machine_dynamic (void)
>>+{
>>+ return _GLOBAL_OFFSET_TABLE_[0];
>>+}
>
>_GLOBAL_OFFSET_TABLE_[0] == link_time_dynamic is not recommended.
>See
>https://maskray.me/blog/2021-09-05-build-glibc-with-lld#global_offset_table_0
>aarch64/riscv/x86_64/etc have been updated to use the preferred
>approach.
>
>Fixed.
>
>
>diff --git a/sysdeps/loongarch/dl-machine.h b/sysdeps/loongarch/dl-machine.h
>index f902410213..361f7555f9 100644
>--- a/sysdeps/loongarch/dl-machine.h
>+++ b/sysdeps/loongarch/dl-machine.h
>@@ -70,28 +70,18 @@ elf_machine_matches_host (const ElfW (Ehdr) * ehdr)
> return 1;
> }
>
>-/* Runtime address of .got */
>-#define _GLOBAL_OFFSET_TABLE_ \
>- ({ \
>- ElfW (Addr) * r; \
>- asm("la.pcrel %0, _GLOBAL_OFFSET_TABLE_" : "=r"(r)); \
>- r; \
>- })
>-
>-/* Return the link-time address of _DYNAMIC. */
>-static inline ElfW (Addr) elf_machine_dynamic (void)
>+/* Return the run-time load address of the shared object. */
>+static inline ElfW (Addr) elf_machine_load_address (void)
> {
>- return _GLOBAL_OFFSET_TABLE_[0];
>+ extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
>+ return (ElfW(Addr)) &__ehdr_start;
> }
>
>-/* Return the run-time load address of the shared object. */
>-static inline ElfW (Addr) elf_machine_load_address (void)
>+/* Return the link-time address of _DYNAMIC. */
>+static inline ElfW (Addr) elf_machine_dynamic (void)
> {
>- ElfW (Addr) got_linktime_addr;
>- asm("la.got %0, _GLOBAL_OFFSET_TABLE_"
>- /* Link-time address in GOT entry before runtime relocation */
>- : "=r"(got_linktime_addr));
>- return (ElfW (Addr)) _GLOBAL_OFFSET_TABLE_ - got_linktime_addr;
>+ extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
>+ return (ElfW(Addr)) _DYNAMIC - elf_machine_load_address ();
> }
Thank you. The updated elf_machine_load_address and elf_machine_dynamic
look good.
@@ -70,28 +70,18 @@ elf_machine_matches_host (const ElfW (Ehdr) * ehdr)
return 1;
}
-/* Runtime address of .got */
-#define _GLOBAL_OFFSET_TABLE_ \
- ({ \
- ElfW (Addr) * r; \
- asm("la.pcrel %0, _GLOBAL_OFFSET_TABLE_" : "=r"(r)); \
- r; \
- })
-
-/* Return the link-time address of _DYNAMIC. */
-static inline ElfW (Addr) elf_machine_dynamic (void)
+/* Return the run-time load address of the shared object. */
+static inline ElfW (Addr) elf_machine_load_address (void)
{
- return _GLOBAL_OFFSET_TABLE_[0];
+ extern const ElfW(Ehdr) __ehdr_start attribute_hidden;
+ return (ElfW(Addr)) &__ehdr_start;
}
-/* Return the run-time load address of the shared object. */
-static inline ElfW (Addr) elf_machine_load_address (void)
+/* Return the link-time address of _DYNAMIC. */
+static inline ElfW (Addr) elf_machine_dynamic (void)
{
- ElfW (Addr) got_linktime_addr;
- asm("la.got %0, _GLOBAL_OFFSET_TABLE_"
- /* Link-time address in GOT entry before runtime relocation */
- : "=r"(got_linktime_addr));
- return (ElfW (Addr)) _GLOBAL_OFFSET_TABLE_ - got_linktime_addr;
+ extern ElfW(Dyn) _DYNAMIC[] attribute_hidden;
+ return (ElfW(Addr)) _DYNAMIC - elf_machine_load_address ();
}